Electrolytic cell



Feb. 16, 1960 c, vE. VAN vwlNczKELl ETAL ELECTROLYTIC CELL 3 Sheets-Sheet 1 Filed June 1,- 1956 v ATTORNEYS Feb 16, 1960 c. E. VAN WINCKELMETAL 2,925,371

ELEcTRoLYTIc vCELL Flerd June l, 1956 3 Sheets-Sheet 2 Feb# 16, 1950 c. E. vN wlNcKl-:L Erm. 2,925,371

ELECTROLYTIC CELL 3 Sheets-.Sheet 3 Filed June 1, 1956 ANoLYTE CATHOLYTE SUPPLY TANK M ,fzmf/ mei ATTORNEYS.

the cathode in a novel way thereby to maintain the cathode chamber temperature within the range which will produce the desired chemical reaction and avoid undesirable side reactions as heretofore indicated. That is, the anolyte is Withdrawn from the anolyte chamber, cooled, and thereafter returned to the anolyte chamber, thereby to maintain the anolyte chamber at a temperature Vsubstantially below that of the catholyte. The surface to volume relations of the cathode chamber are so high and hence the potential heat interchangeable between the anolyte and the catholyte through the diaphragm are such that the temperature of the catholyte in the cathode chamber may .be controlled by circulating the anolyte through the anode j chamber as described, and cooling the anolyte before 1t is returned to the anode chamber.

Certain features of the invention including the .procedural features and the manner of cooling the anolyte i' preferably stainless steel or other conductive material will be better understood after considering the following Y- description taken in conjunction with the accompanying drawings.

Figure 1 is a perspective view,- with parts omitted, of a electrolytic cell and liquid supply means embodying one form of the invention for the electrolysis of organic compounds.

Figure 2 is a sectional side view at 2-2 of Figure 3.

Figure 3 is a sectional view at 3-3 of Figure 2.

Figure 4 is an enlarged sectional view at 4-4 of Figure 2.

Figure 5 is a perspective view of a cathode compartmentl frame and cathode. of the invention.

Figures 6 and 7 are sectional side views of other embodiments of cell units of the invention.- l

Figure 8 is a partially schematic illustration of the assembled cathode, diaphragms and anode of the invention with the apparatus which is usedin circulating and cooling the anolyte 'and' catholyte. j

Figure 9 is a detailed view of a perforated platewhich may be used on the cathode instead of a screen.

The electrolytic cell unit illustrated in Figs. 1 to 5 comprises several cells each consisting of an anode and anode compartment 1 `on each side of a cathode and cathode compartment 2, `with a diaphragm 3 between the cathode and anode compartments and a coolant cham- 'ber 4 between the adjacent anodes. Each member of the unithas the same rectangular cross-sectional shape and Vd-imensionsso that the cells may be arranged in series anolyte drain connection 8 at the bottom of the frame which connects to the anolyte drain pipe. The anolyte may be under such a pressure that it stands in pipes 7 up almost to the `anode compartment .ventpipe We prefer to construct tubes 7, 8 and the anolyte drain of a nonconducting material such as furfuryl alcohol Vresin tubing or pipes. The projecting lugs 9 include any suitable means lfor connecting the anodic plates to the electrical circuitl.V v

The diaphragms 3 are preferablyV formed as a Aiiat sheet consisting of fibrous material bonded with furfuryl alcohol resin and otherV resin, such as described more fully and.claimed in copending application SerialNo. 405,038, tiled January 19, .1954,V and now abandoned..

The cathodes 11 of the combinations 2, comprise oper- Y ating 'and supporting rods 12 to whichare permanently attachedperforated spaced plates 13 'which providea that is refractory to the catholyte. The cathode is `supported within the space 15"inside the cathode compartment frame 16, which is mounted between adjacent diaphragms 3. The frame 16 is provided with an inlet connection 17 for the supply of catholyte and an outlet connection 18 for the removal of catholyte from the space 15. It will be noted that the cathode is arranged to reciprocate while being entirely immersed in the catholyte.

The coolant members 4 consist of rectangular Vframes 19, also preferably formed of furfuryl Valcohol resin, having interior spaces 20 for the circulation of the coolant which Vare closed 4oi by the adjoining plates 6 of the anodes. The frames,19 have inlet pipe connections 21 at the bottoms and outlet pipe connections 22 at the tops for the circulation of any suitable nonconducting liquid such as lubricating oil fromY the coolant main.

The furfuryl alcohol resinpframesV are advantageously formed according to the method of copending application Serial No. 405,038, filed January 19, 1954, and are preferably lled with various materials, such as asbestos.

-The furfuryl alcohol resin of which this cell is largely constructed has unique properties for the purpose of this tures up to C.

The assembly of a cell unit is arranged with the cells alongside of each other, repeated one after the other, and the entire assembly is held in a rigid horizontal position in a frame F which is similar to a ilter press skeleton. Between the adjoining faces of the members, any, suitable gasket, such as asbestos tape G, is interposed and the screw means S presses the members into fluid-tight contact with the gaskets, thereby vsealing the compartments from each other. Instead of a gasket, we may use a sealing resin or inert plastic material.

The cathode rods 12 pass through stuing boxes 21 and are connected by stirrups 22 to the lift rod 23. A layer of electrical insulation 24 is interposed between the stirrups and the rod 23. The bearings 25 guide the rod 23 in its up-and-down movement on the guide rods 26. The rod 23 is operated by the links 27, crank arms `Z8 and rotatably driven shaft 29. The cathodes .-11 are Aty any convenient places on the rods 12 conductor clamps 30 are attached for connection to the flexible electrical conductors 3l which lead to the anode conductors A10 of an adjacent cell.

In the more complete embodiment of apparatus shown somewhat diagrammatically in Figure l, the catholyte inlet connections 417 are connected by short sections of nonconducting tubing such as furfuryl alcohol resin tubing or hose 32 to the catholyte supply pipe 33 which is supplied from the tank by the centrifugal pump 34. The catholyte circulates through the cathode compartments and leaves through the furfuryl alcohol resin tube sections 35 which connect the outlet connections 18 to the yreturn main 36. The catholyte in the tank'is preferably agitated with any suitablevdevice and cooled by means of a heat exchanger if desired. The anolyte drain pipes 8, the catholyte supply pipes 32, and outlet pipes 35 are preferably of such small diameter, around 1/2 to l inch, and lsuch length, around 2 to 4 feet, that the catholyte therein olers such high resistance that therer is practically no current flowing in the anolyte drain and catholyte supply and return pipes. The catholyte circulating supply tank and the sections of pipes 37 and 38, as well as the pump 34, are also formed of stainless steel.-

The alloy, Inconel is especially suitable for the p anodic'plates. It showed no`corrosive action when used for 250 ampere hours at a current 'density of V2,1 amps/dm?. |It has also shown no attack when used re An electrolytic cell of peatedly in acell of our., iriventionfoperatingat approxiure .2 isformed so that it WilltranSmitfiQns withoutfperinittig'the passage of'particleswhich are dispersed but not dissolved,` e.g.,. insoluble organic compoundsof the ltype which may be red'ucedby'electrochemical methods.

each. side of the vdiaphragm,r and a sheet of expanded Y metal ,142" on'the exterior side` off'each screen.v

The electrolytic reaction may becarriedout by retaili-I ingall ofthe catholytein the, cathode chamber until operation is complete andithen. draining the 'reaction product from the charriber.4 However; itis preferred to circulate the Vcatholyte through the. cathode vcl'ia'rriber during the operation and' for this purpose. therelisprovided. in Figure 8 a pipe 1451 of"nonc'ond` u cti'1 ig'material'y leading toz a catholytefsupply tank '14 6; ,From the supply tank, ca ztho-V a .6001er or. heatinterchanger .150;{and`backt the catiidde.

'chamber through anotheijnonconductirigfpipe 151.;

The anolyte in the anode chamber-:is also withdrawn through the pipes 152 which-arev formed of nonconducting. material to an anolyte supply. tank 1755.,` Fromthe;`

' `30 omit the coolant compartment and form theanode of a tank 1 55 the anolyte passesutliro'ligh the `p unipl156, .the cooler or heat interchange; f15 7 and back to the anode chambers through the pipes 16,0?? valso madev of nonconducting material.

The vanode frame and chamber shown'inFig'ure 8in-.

' 35 ciprocably mountedl on the rod 53 in. a manner similar clud'es. a centrally disposedY liquid impervious `web 122 whichv forms two anode. chambers 125. and 1 2`6', one-.on each side ofthe web. Each chamber has an anode plate 130 .or 130' mounted thereinand secured toftheweb 122.

The conductor bars 13 1 supply the electric current` to f 40 all .rectangular in. cross-sectiony and formed preferably the anode plates.- The manifolds 116 may be usedto supplyanolyte or. catholyte .to the respective compartments, through connecting pipingl not shown. Another Y cathode chamber not shown maybe provided to the right ofthe anode chamber anddaphragm shown in FigureS,

o0. i s s 'ea1ed` between the frames 56 and: 57". The cathode and another anode chamber tothe left of the cathode chamber and diaphragmthereofl Y As heretofore indicated a serious problem in carrying out electrolytic processes is the'control of the tempera- Iture to produce the desired product. of the liquidl in the cathode chamber is small and the amount of heat generated relatively large, temperature control isv diiiicult. It is an. outstandingV feature of the presentinvention. thatan improved way isv provided to control .the .temperature of the catholyterinfthe'cathode 55 made ofy granularfurfuryl resin, as previously described,

chamber in the operation of an electrolytic cell. This is accomplished by providing anY electrolytic cell'v having a cathode andan anode in which the'catholyte and anolyte are in direct contact withloppositesidesfof a semiperof the relatively large area-to-volume relation `between i diaphragm and. th'e'volume o'ftliefcathode chamber to transmit ht through the diaphragm from the catholyt .to theY anolyte, thereby maintaining. temperatures, the cathode chamber which are more nearly uniform and within the desired range for optimum control of the 'electrolytic reaction. Y K' j e inventionespecially Asuitable forV the reduction of o rthonitrochlorobenz'ene has cell units of the approximate following dimensions:

' inches) camara .i

Since the amount 63 which 1s moved up and down by the rod 64. The

70 `from the product.

By the addition of small amounts of, lead, i.e., 25

Overall" outside height'v 12 to 30 Y `inllesl. f

Anode frameabout-l'to 2 inches thick' Cathodeconipartnient frameabout 11/2 to 3 inches thick inches (inside 1Q to vi Coolant conji'p'artrnentV frame about toill/z 'inches thick Diaphragm Yalsioiit 1A 'to 1/2" inch thick .nodiQPlate about 1A.' to 1/2v inch thick is to: ybe` understood that these are not limiting i0 specifications since the cell'and cathode can be offany suitable` dimensionsiwithin the inventive con'ceptde scribed*herein. z' In a cellhaving outside cross-sectional *diirierisions;offv 12 by ll2 inches', the cathode compartment .hasta'n inside square dimension of 10 inches and theV 15 'cathodej is'f91/a inches-'wide by 4 inches high -by 1% 'inches thi'clcand" canbe moved inthe cathode chamber v'vithoutncontactingy the compartment frameVA or the diaphragm. Themodiication'of cell unit illustratedlin Figure somprisesyananode .samrartmentframe 45 a Cathode l20 "compartmenttframef-t; and-a coolant compartment-frame 4 7; all rectangular lincrosss ectiom and preferably` formed of fjirfi'iryl'i' alcohol resin. The Yframes are provided with inletV and outleconcctions for vthe circulationl of anolyte,

v catholyte and coolant as in Figure 1. The .anodic plate k the'diaphragm issealed betweeny theframes 45. and

' inertwjalif memben 'which` closesconje side'of thecoolant compartment onjone' sideofJ the anodicl plate 48. We

coil of Inconel tubing and1 cool the' anode byfcirculating thecoolant therein. We may'also eliminate the coolant members entire ly and circulate the anolyte to a heat 'exchangeras .described above. The cathode l52 is re- "Ifhemoditication of` cell unit illustrated in Figure 7 comprises anode compartment frame g cathode Vcompartment frame 56, and coolantcompartment frame`57,

to" the 'cathode of Figure. 1'.

'comprises a stainless steel plate 61 which 'seals the Vcathode compartment from the coolant compartment and an active, cathode .member 62 of stainless steel mesh. The 'catholyte is agitated with the'stainless steel agitator anodei cathode, and' when provided the coolant compartments have inlet and'outlet means, as in Figure 1,

`for thecirculation` of anolyte, catholyt'e, and coolant.

The. diaphragms ofv Figures 6 and 7 arepreferably electrolytically deposited on the stainless steel.' As stated `abovgkthe cathodic[element comprises a stainless steel generally theybringabout reduction of nitro compounds at high currentfeiciencies. Meshes lower than 80 gradudecrease their 4ability@ to produce' complete re'- duCtiOn.. 1Q. .thehydrazo compoundv as evidenced by f in- 'creasingtamounts .of azoxyand azo intermediate isolated the sponge 1ea`d,'or by adding lead'to the cathode in other `long life.

in rectangular cathode compartments, withmeans for,

were converted to the materials designated:

-. ways, an improvement in reducing the nitro compounds .large number of cells that may be connected in series. i.

In fact several cell units may be connected in series to utilize even higher voltages. The construction of the cell also makes possible better and more uniform mixing of the charge and provides a ready means of controlling the temperature and of charging and discharging the cells without an undue loss of current eciency. ,A Otherimportant features are the low resistance per cell, comparatively cheap construction, ease of maintenance, and Moreover, the rectangular cathodes, operable reciprocation in an up-and-down movement permits the use of an elongated narrow cell unit which may be employed in banks of 10 to 12 cellnunits, each connected in series.

l One important feature of the invention is the adaptability of the units to operation in a series circuit. v In connecting ythe individual cells in `series it is possible to use highvoltage current, the voltage across each cell being from 3.5 to volts. Several units, each having several Icells may be connected in series giving the advantage of using relatively high generator voltage. It is advantageous to connect the anodes on each side of a cathode in parallel and the cathode in series to the next pair of anodes and so on through the series. In this way the electron movement is from a cathode toward the adjacent side of each anode.

Example I i The following is an example of an operation carried out in 30 inch cells of the type described in Figures 6 and 8 which are provided with reciprocating cathodes having 8O mesh stainless steel screen. Theratio of the elfective cathode chamber volume to the cathode screen surface area was 684 cc. per square decimeter. The catholyte solution was prepared by mixing` orthonitrochlorobenzene with 10% aqueous sodium hydroxide in the ratio of one part of the nitro compound to five parts of the aqueous caustic. The internal temperature in the electrolytic cells was raised to about 90 C. (by circulating and heating the anolyte and catholyte in the heat exchangers), and the organic matter was dispersed in the catholyte by reciprocating the cathodes at ythe ratev of about 150 cycles per minute in strokes of about 4 inches. Direct current was applied across the unitof cells connected in series and the voltage was controlled to provide a current density of 11.7 amp. per square decimeter of cathode screen area per cell. The tempera ture inthe cathode chamber during the reaction was maintained at 90 C. by circulating and cooling the anolyte and catholyte in the external heat exchangers shown in Figure 8. After 104% of the theoretical current which is required to reduce the orthonitrochlorobenzene to 0,0'-dichlorohydrazobenzene had passed through the cell, the catholyte which was then. colorless,

Ywas discharged from the cells and the o,o,dichlorohy drazobenzene was recovered by solvent extraction'. The byproducts orthochloroaniline and orthodichlorobenzene were also recovered. The analysis showed that the following percentages of the orthonitrochlorobenzene Percent To 0,0'-dichlorohydrazobenzene v80.8 To o-chloroaniline 5.7 To o,odichloroazobenzene 13.5

Example Il .The following is an example of the operation carried out in the apparatus of Figure l. The anode compartments of .the cells are chargedwith 30% aqueous caustic soda solution. Next 7,000 parts of 10% caustic soda so- ,lution is placed in the steel catholyte circulating tank circulating system was 3:1;

and is heated to 90 C. Circulation and agitation is then started and continued until the cell is heated Vas indicated by the temperature of the returning solution. 1000 parts of orthonitrochlorobenzene is then added to the .catholyte Vcirculating' Ytank and the current is passed through the cells at a density of 4 amps/dm?. It is desirable to control the ratio of nitro compound to caustic solution within certain limits. For best results a ratio of nitro compound to 10% caustic solution of not greater than about 1:5 is used. Although the lower limit of this ratio is not as critical, ratios of at least about 1:15 are preferred. The temperature during the reduction is maintained at 90 by cooling both the anode compartment and the catholyte in the catholyte tank. When the reduction is about 75% complete, hydrogen may be evolved and the current can be reduced, if desired, to prevent excessive 'hydrogen evolution land to obtain greater current etiiciency. When the reaction is complete as indicated by the rate of evolution of hydrogen, the passage of'about 110% of the theoretical current and '..the color change from orange toyellow, the current is I'shut olf and the cells drained into the catholyte tank.

,Agitati'on is stopped and the molten hydrazobenzene or a derivative thereof is allowed to settle and is then drawnroff. The remaining caustic solution may be adjusted as to strength and reused or discarded.

Example III.

The procedure described in the preceding examples was repeated using a three-cell unit, of the type deorthonitrochlorobenzene was mixed with the aqueous caustic in the ratio of 1:5.5, the amount of catholyte provided was such that the ratio of catholyte in the cathode chambers to the amount of catholyte in the external The current density was 11.2`.amp. per squaredecimeter of cathode screen area. After 132% of the amount of current theoretically necessary to reduce all of the nitrochlorobenzene to dichlorohydrazobenzene had been passed through the cells, the operation was discontinued ,and thecatholyte analyzed for materials described in Example I. It was determined that the following amounts of orthonitrochlorobenzene were converted to the materials designated:

Percent To o,o-dichlorohydrazobenzene 80.7 To o-ch1oroaniline 10.9 To o,odichloroazobenzene 8.4

Following are examples of other materials that have been successfully reduced using the procedure and apparatus described in Example I:

Reactant I Catholyte Product Nitrobenvnn Caustic Hydrazobenzene. o-Nitrotoluene Caustic- Azoxytoluene. o-Nitroanisole Caustic Hydrazoansole. Nltrobenzene 20% HzSOl'. p-amlnophenol.

A* mesh Monel screen cathode.

asaaai l tions and equivalents be included within the seopeiof the appended claims. 's y We claim: f i Y 1 Electrolytc apparatus comprising an upright, gen- 'e'rally rectangular hollow cell frame having an axis perpendicular to the plane of the rectangle and at least one open side of relatively large dimension as compared with the axial frame thickness,- said frame enclosing a cell `chamber for containing a catholyte .comprising an aqueous suspension of a reducible, organic compound that is insoluble in the aqueous suspension,an .electrode` housed within said cell chamber mounted forvertical reciprocation and attachedv toV means for reciprocating 1 liquid-tight relationship with respect thereto, said eleciV trode comprising `a frameworkfand a `screen supported by said lframework having Va'rrleslr size in therangejfrom about 20 to 120, so that reciprocation of said electrodeY maintains said organic compound dispersed inthe catholyte and mixes the dispersed material uniformly'into all portions of said cathode chamber. p f I V2. The apparatus desc` `'bed in claimV 1 wherein the mesh size of -t'he screen is in -the range from about 80 to 120.'. Y 3. The apparatusdescribedin claim 1'-l comprising an anode cell frame enclosing `an anode ychamberson theside of said diaphragm'oPPOrSite vtofsaid cathode chamber,

anode `chamber containing liquid anolyte, means for Wittidrawing said anoly'te from said anode chamber, means for cooling `said anolyte externally of said 'anode chamber and means for returning said cooled anolytey to said anode chamber thereby' to control the temperature'vof the catholytein the cathode chamber lby heat transfer to the fanode chamber through the diaphragm.

4. The yapparatus described in claim 3 including means -for withdrawing the catholyte from the cathode chamber, f means forv cooling 'said withdrawn catholyte externally of thecathode chamber and means for returning cooled -catholyte tov thecathode chamber.

Y The apparatus'describedrin'cl-aim l in `which the screen stainless steel. Y References Cited in the le of this patent UNITEDA STATES PATENT-s the 736,206' Y -Buchner Aug. l1, .1903,V 1,074,274 MacKay "....e Sept. 30,1913 1,075,362 Ma'rsh Oct. 14,51913y :1,225,052 Pigl'let May 8, 1917 V2,110,273r McKee 1 Mar.Y 8, 1938 2,289,189` Hales f a July 7, 1942 2,589,635 Smith etal. Mar. 18, 1952 2,681,887 Butler June 22, 1954 .l v FOREIGN PATENTSy y 20,192 'Great Britain Apr. 28, 1910 UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 2,925,371 February 16il 1960 Carl E. Van Winekel et al.,

It is herebb't certified that error appears in theprinted specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3., line 65, for' "and other"l read or other --g column 6Y line 23, for "collections" read connections line 30Y before "vomit" insert may Signed and sealed this 9th day off August 1960.

(SEAL) Attest:

KARL He XLINE` Attesting Oficer ROBERT C. WATSON Commissioner of Patentsl 

1. ELECTROLYTIC APPARATUS COMPRISING AN UPRIGHT GENERALLY RECTANGULAR HOLLOW CELL FRAME HAVING AN AXIS PERPENDICULAR TO THE PLANE OF THE RECTANGLE AND AT LEAST ONE OPEN SIDE OF RELATIVELY LARGE DIMENSION AS COMPARED WITH THE AXIAL FRAME THICKNESS, SAID FRAME ENCLOSING A CELL CHAMBER FOR CONTAINING A CATHOLYTE COMPRISING AN AQUEOUS SUSPENSION OF A REDUCIBLE, ORGANIC COMPOUND THAT IS INSOLUBLE IN THE AQUEOUS SUSPENSION, AN ELECTRODE HOUSED WITHIN SAID CELL CHAMBER MOUNTED FOR VERTICAL RECIPROCATION AND ATTACHED TO MEANS FOR RECIPROCATING SAID ELECTRODE IN A DIRECTION PERPENDICULAR TO SAID AXIS, A DIAPHRAGM SECURED AT SAID OPEN SIDE OF SAID FRAME IN LIQUID-TIGHT RELATIONSHIP WITH RESPECT THERETO, SAID ELETRODE COMPRISNG A FRAMEWORK AND A SCREEN SUPPORTED BY 